A numerical investigation on the heat transfer and turbulence production characteristics induced by a swirl spacer in a single-tube geometry under single-phase flow condition

Y Heat transfer in the rod bundle is augmented by the mixing vanes on the spacer grid. We conducted a computational fluid dynamics (CFD) simulation with three isotropic turbulence models - standard k-epsilon, realizable k-epsilon, and SST k-omega models - to investigate the relationship between heat transfer and turbulence behaviors downstream a simulant spacer (with four vanes) in a single tube under single-phase flow conditions. Quantitatively, the predicted heat transfer coefficient (HTC), secondary flow intensity, and turbulence intensity with the SST k-omega model displayed a better agreement (than the other isotropic models) with the experimental data in previous studies. Moreover, the turbulence production was localized in the near-spacer region (z/D < 10, where D is the inner diameter), which corresponds with the HTC augmentation region. These results indicate that examining the turbulence production when discussing the HTC augmentation downstream the spacer is essential. (C) 2021 The Author(s). Published by Elsevier Ltd.